Cats do urinate in their own beds.
I have a 14 year old female cat who will thoroughly enjoy her bed for a day or so, then she'll squat and urinate in it. At that point, she'll abandon the bed alltogether until I wash it again. I blamed the other cats for the longest time until I personally witnessed her urinating in her own bed several times.
I purchased some Feliway spray and will try spraying her bed and the area to calm her anxieties down. I have the feeling she's stressed over other cats being in the house. All of the kitties get love, pets and attention, so she must be stressed.
I'm hoping that the Feliway spray will solve the problem.